Deer and the Population Problem

Deer in an Ann Arbor back yard, winter 2016

We have been posting about Ann Arbor’s deer herd and the issues it raises since last December (see our summary page, What Do We Do About the Deer? for a list of posts and also useful resources and links to news articles). There are many reasons to be concerned about the size of the herd.

Deer-Vehicle crashes. According to SEMCOG, there were 952 reported deer-vehicle crashes in Washtenaw County for 2014 (33 injuries), and 51 (1 injury) in Ann Arbor. Anecdotally, there are many more “near misses” where drivers avoid a crash but not an adrenaline rush. (The numbers reflect only reports made to the police.)

Lyme Disease. (Be afraid. Be very afraid.) The presence of Lyme disease in humans and the prevalence of deer are closely correlated. Lyme is a truly scary disease that is curable by antibiotics if caught in the early stages of infection. Often, however, the disease is not detected early and may even be mistaken for other diseases. In its chronic form, it has long-lasting neurological effects. This is not just another little “bug” that most people get over easily. It can be life-changing.

The migration east of Lyme Disease. Note that Jackson County is now shown as potential though unconfirmed.

Lyme disease has affected some individuals in Washtenaw County but there are no verified cases of transmission here as yet. In order to verify transmission, the tick itself must be sent to a laboratory and tested for the presence of the bacterium. It is assumed that all current cases in the county originated from an infection elsewhere. However, according to the State of Michigan, Lyme disease is an “emerging disease” and is steadily moving eastward from southwestern Michigan, where it was first described in our state. How is it moving? Deer (they don’t recognize county boundary lines).

Shamefully, individuals who oppose lethal culling in Ann Arbor have made the technically accurate but misleading statement that “deer don’t carry Lyme Disease”. Lyme is an infectious disease caused by bacteria that are carried by deer ticks (black-legged ticks). It has a complicated disease cycle. Young ticks (nymphs) exist primarily on rodents, especially the white-footed mouse. The mouse is the reservoir host for the Lyme disease bacterium and does not appear to be harmed by the infection or the tick burden. The ticks climb onto deer as adults for their blood meal prior to reproduction. Deer carry them into human contact. Without deer in the neighborhood, Lyme Disease transmission would occur very rarely. There is general agreement that Lyme disease incidence and deer density are strongly correlated. In one important study, a severe reduction in deer density reduced the number of cases in a Connecticut community markedly. The deer population was reduced by over 80% by a hunting program, to about 5 deer per square kilometer (just over 12 per square mile). The incidence of Lyme Disease was reduced by 80%.

“Reducing deer populations to levels that reduce the potential for ticks to successfully breed should be an important component of any long-term strategy seeking to reduce the risk of people contracting Lyme disease,” they concluded. “Additionally, good hunter access to deer habitat and a wide variety of management tools (bait, unlimited tags, incentive programs) are important components of a successful deer reduction strategy.”

This video has good pointers on how the presence of Lyme-bearing ticks can modify the way you can enjoy the out-of-doors. It is also a good review of Lyme disease, the deer-tick-mouse equation, how to deal with ticks that you bring home, and other good information. Really, it is worth your time. Beautifully produced with views of Nantucket.

Our Natural Areas. Ann Arbor has invested a great deal of money both to acquire our natural areas and parks and to maintain them. We have hundreds of volunteers who turn out to remove invasive shrubs and do other maintenance tasks. One reason for this is that many of us appreciate the natural world, including not only the flowers and trees but the birds, insects, small mammals and the sometimes miracle of frogs, toads and salamanders. In preserving the natural areas, we are creating a living collection of life. As our previous posts Deer and the Web of Life and Deer and the Flowers of Earth have expressed, burgeoning deer populations are a threat to the entire ecosystem. This has been shown in study after study nationally, and we have some local studies too. Deer are explosively fecund and their population increases geometrically, as we explained in Deer and the Numbers Explosion. They don’t give the rest of the living world much of a chance.

A swallowtail butterfly caterpillar in an Ann Arbor backyard

Our Gardens. People who are not gardeners or who do not maintain a landscape are often dismissive of those who care about plants in their own backyards. It is hard to express the anguish of losing a cherished plant to those who simply don’t regard this as important. And the thousands of dollars lost in landscape damage is dismissed by commenters as “rich people worried about their…” Yet these are heartfelt losses. And I would also plead that our backyard flowers support a lot of wildlife, beginning with insects (pollinators are in vogue just now; even President Obama is on their side) and birds who love the nectar, the seeds, and the insects that garden flowers provide.

This squash plant has been stripped of all flowers, fruits and growing tips

A previously productive vegetable garden that once fed a family has been occupied by a deer herd

Even more basic is the human need to be able to raise vegetables from one’s own soil (or in a public garden). The Ann Arbor deer are now affecting community gardens maintained by Project Grow and have caused what I will term as tragic losses to home vegetable gardeners in some locations. I myself have had to surrender my vegetable garden, though it was of great importance to me. (My garden blog was almost all about vegetables.) The pictures shown here were of an extensive vegetable garden on the east side of Ann Arbor that is now in ruins, an occupied territory. The unsympathetic who suggest “planting resistant plants” haven’t considered that we have selected food plants over millennia to be highly edible, and the deer are happy to participate. When deer attack them, they eat the tender growing parts, the buds, young leaves, developing fruits. They devastate the crop.

Basic safety. In addition to all these problems, it should be noted that these are large animals with sharp hooves, and, in the case of bucks, antlers. It is not possible to confront them in person. There are stories which I will not attempt to document here of attacks on pet dogs, intrusions on decks, and other threats to personal territory.

So what are we to do? It is clear that we need to limit (reduce) the deer population in Ann Arbor. They are beginning to penetrate even to neighborhoods where they have not been seen until recently. But they are virtually an occupying force in some areas. The City Council and Administration have recognized that something must be done. After a nearly year-long process including much public participation, a staff report recommended a management program which included a lethal cull to be conducted under very restricted conditions. (NOT hunters in your backyard.) There was pushback. A special work session was called in which the Humane Society of the US was given an opportunity to present information about the “nonlethal” approach of using experimental contraception and/or surgical sterilization instead. The presentation is here. Now it has been announced that the City Council will consider a resolution on August 17, 2015. The method of limitation of the deer population that will be proposed has not been announced. There will also be a public hearing at that meeting. Any Ann Arbor resident may speak on this topic without signing up ahead of time. The actual text of the legislation will by that time be available on Legistar. UPDATE: Here is the text of the resolution as amended.The Council voted 8-1 to conduct a lethal cull in winter 2016. Mayor Christopher Taylor opposed this. The resolution was amended to indicate that the City would also cooperate with a study of sterilization or contraception if practicable.

Soon we will know what our City will do to address this real and present problem of excess deer population in Ann Arbor.

UPDATE, January 2016: Ann Arbor is now conducting a lethal cull of 100 deer in 14 city parks. City Council passed several enabling resolutions, listed here.

ADDENDUM: One of the best examples of a deer management plan in our area is that practised by the Huron-Clinton Metroparks. This organization manages many significant open spaces throughout SE Michigan. They long ago recognized the importance of deer to their overall management of these areas. Here is their latest Huron Clinton Deer Plan (July 2015).

SECOND ADDENDUM: Local author and journalist Margaret Leary has compiled a summary of deer-vehicle crashes over the last 10 years. She also calculated the percentage of vehicle crashes related to deer. Sure enough, the percentage has increased over the time period.

THIRD ADDENDUM: Data obtained by the former editor of the Ann Arbor Chronicle (Dave Askins) indicates that the number of deer-vehicle crashes has shot up dramatically in the last year, to 88 total reported in Ann Arbor.